1. Field of the Invention
The present invention relates to an ink cartridge, and particularly relates to an ink cartridge capable of reducing the ink capacity without changing the shape of its casing and capable of suppressing deterioration in degree of deaeration of ink.
2. Description of the Related Art
There has been hitherto known inkjet recording apparatus in which a black ink cartridge and a color ink cartridge are mounted so that ink is supplied from each ink cartridge to a recording head, and the ink is ejected from the recording head to a recording medium. In this inkjet recording apparatus, color ink is less frequently used than black ink in the use condition where the greater part of print data is text data. Thus, the validity of the color ink expires before the color ink is used up. As a result, there is a problem that the color ink cartridge is obliged to be exchanged for a new one so that the running cost increases. On the contrary, the black ink is less frequently used than the color ink in the use condition where the printing amount of color images is large. Thus, the validity of the black ink may expire before the black ink is used up. Further, when the inkjet recording apparatus itself is not frequently used, the validity of each ink may expire though both the black ink and the color ink are still in existence.
In order to solve the problem, it can be considered to manufacture an ink cartridge whose volume is reduced to reduce the ink capacity. However, there is a problem that a mold of such a low-volume ink cartridge has to be built up so that the cost increases. In addition, to mount the small ink cartridge on the inkjet recording apparatus, the shape of the mounting portion have to be changed. Thus, there is a problem that the cost increases more.
JP-A-9-262988 proposes an ink cartridge in which filler is charged into a bottom portion of a container forming a normal volume of the ink cartridge so as to reduce the ink volume. According to this ink cartridge, the ink filling amount can be reduced by charging the filler without changing the shape of the container. However, the shape of a porous material near an ink supply port is deformed. The ink supply port has the strongest influence on the ink outflow property with which ink flows into the recording head. Thus, there is a problem that there may occur a fluctuation in the print properties.
JP-A-2001-121715 proposes an ink cartridge including a container body communicating with an ink chamber through a supply port, a porous material to be impregnated with ink being received in the ink chamber, and a cover for sealing an opening portion of the container body, wherein a spacer is attached between the cover and the porous material. According to this ink cartridge, the ink filling amount can be reduced without changing the shape of the container while keeping the ink outflow property.